Identification and function of type IV IFN, IFN-υ and its receptor subunits, IFN-υR1 and IL-10RB in chicken Gallus...

Interferons (IFNs) are central cytokines orchestrating antiviral innate immunity across vertebrates. Type IV IFN represents a recently identified and evolutionarily conserved IFN family. But, its molecular characteristics and biological functions in poultry species remain incompletely understood. In this study, we systematically identified and characterized chicken (Gallus gallus) type IV IFN, IFN-υ, together with its receptor subunits IFN-υR1 and IL-10RB, and investigated their evolutionary features, expression pattern, receptor distribution, and antiviral activity. Synteny and phylogenetic analyses demonstrated that chicken IFN-υ is embedded within a highly conserved genomic locus and clusters distinctly within the type IV IFN lineage, clearly separated from type I, II, and III IFNs, while sequence analysis revealed conserved structural hallmarks, including an N-terminal signal peptide, a conserved sequence CXXXXX[W/L], an invariant C-terminal CAWE motif and a predicted multi-helix structure. Quantitative expression analyses showed that IFN-υ is constitutively expressed in multiple chicken tissues, with relatively higher basal levels in immune-related and mucosal organs, and is differentially induced by poly(I:C) stimulation in a tissue- and time-dependent manner, whereas both receptor subunits were ubiquitously expressed and dynamically regulated following poly(I:C) challenge. Recombinant chicken IFN-υ was successfully expressed and purified as a monomeric protein and effectively induced representative IFN-stimulated genes (ISGs), confirming its biological activity. Importantly, IFN-υ significantly suppressed Tembusu virus (TMUV) replication by inhibiting viral gene expression and markedly attenuated virus-induced cytopathic effects (CPEs) in vitro in a time-dependent manner. Collectively, these findings establish chicken IFN-υ as a functional type IV IFN with conserved structural features, regulated expression, defined receptor usage, and potent antiviral activity, providing new insights into avian IFN system and highlighting its potential relevance for antiviral immunity in poultry.